The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

NSW govt to pump $1.8bn into WestConnex

NSW Premier Barry O'Farrell and Treasurer Mike Baird are calling on the federal government to contribute some of the $2.5 billion needed to start the WestConnex project.

Mr O'Farrell said the state government would pump $1.8 billion into the project that Infrastructure NSW (INSW) identified as the main priority in a report released on Wednesday.

The $10 billion tollway will link Sydney's west with the airport and Port Botany and will save between 15 and 35 minutes on the journey.

"Even though times are tough, we recognise the need to invest in economic infrastructure to help boost productivity and create jobs," Mr O'Farrell told reporters in Sydney.

While the state government will contribute $1.8 billion to the project, most of the funds are expected to come from a toll, the exact price of which is yet to be announced.

The INSW report said about $2.5 billion would be needed to start the project, and Treasurer Mike Baird called on the federal government to match the $1.5 billion pledged to the project by Opposition Leader Tony Abbott.

"We'll be happy for the federal government just to match what Tony Abbott's (put forward)," he told reporters.